January 18, 2011

Flooding and the Caboolture River

In the recent floods when Beachmere Rd was impassable for several days the Caboolture River appears to have inundated the road to a depth in places of a metre.

The inundation at Caboolture, along Morayfield Rd, was significantly deeper.

I cannot find figures for this latest phenomenon but the excellent resources offered by Bureau of Meteorology -- Flood Warning system for the Pine and Caboolture Rivers -- seems to suggest that the rise at Caboolture must have been in the magnitude of over 9 metres -- thus causing a 'major flood' .

The Caboolture River ... rises in the D'Aguilar Range near Ocean View and flows through Caboolture and Morayfield before entering Deception Bay at Beachmere.The catchment covers 468 km².There are no dams on the waterway, except for a weir and the only major crossing is the Bruce Highway bridge. The Caboolture River is tidal for 19 km upstream to the Caboolture Weir. At the river mouth a sand bar reduces the impact of tidal energy. (ref)

But where does all that water go since at Beachmere no significant events occurred?

Any property owner along Beachmere Rd knows where all that water goes to. It seems that this massive floodplain that surrounds Beachmere protects our sand bar existence from inundation. Nonetheless, if the King Tides had been running up river at the same time as the flood was flowing downstream a wall of more than 2.5 metres high of tidal water would have caused more inundation than was experienced this time around.

If you are interested im what is happening upstream the graphs here -- River Height Data at Haussman Lane -- will give you an idea of the current state of the river on any day.

Click on image for enlarged view

PINE AND CABOOLTURE CATCHMENTS - ASSESSMENT OF THE FLOOD POTENTIAL

The following can be used as a rough guide to the likelihood of flooding in the catchment:

Average catchment rainfalls of in excess of 200mm in 12 hours causes minor to moderate flooding in both the Pine and Caboolture catchments. This flooding will cause minor traffic difficulties as well as inundation of low lying areas.

Average catchment rainfalls of in excess of 300mm in 12 hours causes serious major flooding to occur. Rises in stream height will serverely affect traffic